Cross Linking Among sites
Mood:  blue
Cross linking with a certain group of sites can be sometimes said good but sometimes it is risky too.

It all depends on the site(s) and its value. If the site is expendable, then I wouldn't worry about it much.

Depends upon:
- how many sites
- content overlap
- ownership data
- common code styles/templates across sites
- number and which pages that are linking per site
etc...

There is NO WAY that just linking a handful of sites together - in and of itself - is an automatic problem.

Additional ("negative") factors must be present to create significant risk.

I've seen G take out one spammy site from a mini-net when the others were left standing.

I've seen G take out all but one site from a mini net where there was little dup, but the linking and ownership patterns were clearly designed to inflate PR.

It all comes down to risk/reward. If you have 3 or 4 clean sites and they exist for different reasons and each contains unique content, and they link from a central site's homepage, or just the homepages of each other, that seems pretty low risk to me. (Although, perhaps just slightly riskier than it was two years ago.)

The problem of course is that the filters keep getting more aggressive over time. One never knows when a formerly safe practice becomes a potential red flag or outright problem.

This all may be moot however, since you asked if it is productive. If it doesn't get you much in terms of added PR etc, then I suppose in this environment it's safest to not do it. I just resist being safe for safe's sake.